[MySQL] 事务隔离级别

DataBase Isolation Levels

隔离级别以及对应级别存在问题

Isolation Level/Problem	P0 Dirty Write	P1 Dirty Read	P4C Cursor Lose Update	P4 Lose Update	p2 Fuzzy Read	P3 Phantom	A5A Read Skew	A5B Write Skew
Read Uncommitted	Not Possible	Possible	Possible	Possible	Possible	Possible	Possible	Possible
Read Committed	Not Possible	Not Possible	Possible	Possible	Possible	Possible	Possible	Possible
Cursor Stabillity	Not Possible	Not Possible	Not Possible	Possible	Possible	Possible	Possible	Possible
Repeatable Read	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible	Possible	Not Possible	Not Possible
Snapshot	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible	Possible	Not Possible	Possible
Serializable	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible	Not Possible

隔离级别由弱到强

Degree 0 (everything goes) << Read Uncommitted << Read Committed << Cursor Stability << Repeatable Read << Serializable

这里还有其他2种隔离级别: <font color="green", size="5">Oracle Consistency Read和Snapshot Isolation, Read Committed << Oracle Consistent Read,
Read Committed << Snapshot Isolation << Serializable,
这2种隔离级别都是多版本并发控制机制.

Snapshot Isolation和Repeatable Read并不是对等的, 前者可以防止写偏序(Write Skew), 而Repeatable Read可以防止Snapshot Isolation情况下的一些不能防止的幻读(Phantoms)问题.

隔离级别总结